Motor with toothed disk to secure the stator core

ABSTRACT

The invention relates to an electric motor having a fastening flange 10 and a bearing support part 7 made of plastic or a soft metal, the stator 23 of which is fastened on the outer diameter of the bearing support part 7. At the end of the stator iron core 9, which is on the side away from the flange, a toothed disk 24 made of metal is arranged having radially inwardly extending projections 26 which, in external contact with the bearing support part 7, hold the stator 23. The electric motor 1 can preferably be used in fans.

BACKGROUND OF THE INVENTION

The invention relates to an electric motor having a fastening flange anda bearing support part made of a plastic material or a soft metal Themotor stator is fastened on an outer diameter of the bearing part.

As a rule, the stators of electric motors of this type are glued on abearing support part Before the hardening of the adhesive agent of theglue, the stator must be aligned, and it must remain in this positionuntil the hardening is completed. The apportioning of the adhesive agentmust take place relatively precisely since, due to the small playbetween the inside diameter of the stator iron and the outer jacket ofthe bearing support part, only a small amount of this adhesive agent isrequired It is an important disadvantage of the adhesive agent that theadhesive layer when, for example the bearing support part is pushed on,is pressed away so that no apportioned amount of adhesive agent remains.

The invention is based on the object of eliminating the disadvantageswhich arise as a result of the gluing and at the same time reducing thecosts for the manufacturing of such electric motors. This isaccomplished by means of a very simple mounting.

According to the invention, this object is achieved for an electricmotor of the initially mentioned type by arranging a metal toothed diskat the end of the stator iron on the side away from the flange Saidtoothed disk has radially inwardly extending projections which are inexternal contact with the bearing support part and hold the stator.

By means of a simple axial pressing-on step, the construction of theinventive stator results in the simultaneous fastening and alignment ofthe stator at the bearing support part.

The fastening device provided in the invention is a simple toothed diskmade of strip steel The equidistantly arranged teeth of the toothed diskare made of thin spring steel or strip steel or hard copper, which isthin, elastic and hard, and which are bent away as a result of aresidual spring action to hook themselves in the plastic material of thebearing support part when the stator is pressed on the bearing supportpart. Because of the selected plate thickness of, for example,approximately 0.2 mm, the teeth do not have to be bent forward and thenmounted.

At least one tongue, which projects beyond the outer edge of the tootheddisk, fixes this toothed disk in a position which is appropriate formounting Because of the winding spindle, the teeth should always havethe same position.

A groove, which extends in axial direction in the inside bore of thestator iron, acts in conjunction with an axial cam, extending axially onthe outer jacket of the bearing support part, to prevent any twisting.

For the radial alignment and improved centering, at least three ribs areinjection-molded to the outer jacket of the bearing support part, areapproximately uniformly distributed over the circumference, and extendin parallel to the axis of the inside bore of the bearing support part.

The toothed disk is inserted between the stator iron and the end plateof the winding and is held by the winding of the stator and thus also bythe end plates of the winding. At the same time, the disk is insulatedin the direction of the winding wire.

An axially short smaller diameter of the outer jacket is provided at theend of the bearing support part on the side away from the flange tofacilitate the mounting and provide a space for the raising of theteeth.

Other details and advantageous further developments of the invention arefound in the following description of the embodiments shown in thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a known electric motor;

FIG. 2 is a sectional view of a stator for an electric motor accordingto FIG. 1 mounted according to the invention;

FIG. 3 is a top view of a fastening element used in the invention;

FIG. 4 is a sectional view of an electric motor according to theinvention with a mounted stator installed into an axial fan; and

FIG. 5 is half a top view of an axial fan without the rotor.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a known electric motor 1 consisting of a rotor 2 and astator 3. A shaft 4 is disPosed in bearings 5, 6.

In all embodiments, ball bearings 5 are shown which are fastened in abearing support part 7 made of plastic or soft metal (diecasting).However, sliding bearings may also be used. An iron core 9 of the stator3 is glued on an outer jacket 8 of the bearing support part 7. Afastening flange 10 is used for the fastening of the electric motor 1.In the shown example, the bearing support part 7 and the fasteningflange 10 are constructed as a one-piece plastic molded part.

The drop-shaped rotor 2 of the collectorless direct-current motor shownconsists essentially of a permanent magnet 11 and a return flow pot 12,in the bottom of which, an end of the shaft 4 is concentrically fastenedThe stator iron core 9, which is constructed as a bundle of plates, iscovered on both sides (in axial view) by one winding end plate 13, 14respectively made of plastic. The lower end plate 14 contains at leastthree slotted supports 15 which are arranged approximately in parallelwith the axis. Among other things, the supports 15 are used for thefastening of a printed circuit board 16 which contains the electroniccontrol system for the operation of the electric motor 1.

FIG. 2 shows a stator 23, which corresponds essentially to the stator 3shown in FIG. 1. For this reason identical parts or parts which have thesame effect are provided with the same reference numbers. Thesignificant difference are the devices for the fastening of the statoriron 9 on the outer jacket 8 of the bearing suPport Part 7. A tootheddisk 24 made of thin spring steel or strip steel with a plate thicknessof approximately 0.1 to 0.3 mm and with a central bore 25 is providedwith at least three pointed teeth 26 at the inner edge which arearranged and directed radially to the center of the bore. At least onetongue 27 (in the present example, two tongues) is used for the securingof the toothed disk 24. It projects between the fitted-together windingend plates 13, 14. The outer extent of the bore 25 has a somewhat largerdiameter than the outer jacket 8 of the bearing support part 7, whilethe teeth 26, which project radially toward the inside, areequidistantly arranged on the inner edge.

When the stator parts are assembled, the toothed disk 24 is first placedon the one end of the stator iron core 9, the upper winding end plate 13is fitted over it, and the lower winding end plate 14 is connected withthe upper end plate 13 by means of a sliding fit from the direction ofthe other end of the stator iron 9. Then the stator 23 is wound. Thewinding firmly connects the two end plates 13, 14 and the toothed disk24 with one another by means of the end plates 13, 14. Then the mountedstator 23 is slid over the outer jacket 8 of the bearing support part 7with a slight pressure, until the lower ends of the supports 15 restsagainst corresponding stop surfaces 28 of the flange 10.

The sliding Pressure is exercised on the upper edge 32 of the upper endplate 13. For reinforcing, at least three ribs 33 are injection-moldedon this edge 32 to provide for stiffening. When the stator 23 is pushedon, the teeth 26 of the toothed disk 24, which preferably consist ofspring steel or strip steel with a thickness of 0.2 mm, are bent awayand, after the pressing-in operation is completed, dig themselves intothe outer jacket 8 of the bearing support part 7 made of a plasticmaterial or a soft metal, as a result of the spring-back effectgenerated during the bending-away. This simple and secure fastening fora stator on a supporting part is not limited to supporting parts 7 madeof a plastic material, but can be used anywhere where the supportingpart 7 consists of a softer material than the toothed disk 24; i.e., ofa material into which the toothed disk can penetrate at least slightly.Examples of such materials are "Zamak" (an aluminum alloy produced bydie casting such as ZnAl₄) or aluminum.

An axial pressure is generated from above which affects the insidediameter area of the bundle of plates of the stator iron 9. Thecounterpressure from below takes place at the outer diameter area of thebundle of plates of the stator iron 9 since the supports rest againstthe stop surfaces 28. The spring-back force of the bundle of plates ofthe stator iron core 9, which are bent slightly downward at the insidediameter area, seeks to return into a starting position and, as aresult, additionally presses the teeth 26 of the disk 24 essentially inaxial direction into the outer jacket 8 and thus prevents any axialplay.

For simplifying the mounting, the outer jacket 8 of the bearing supportpart 7, at its upper end (FIG. 2), i.e., on the side facing away fromthe flange, has an axially short area 34 of a smaller diameter.

As a result, the stator 23, without tilting, can be fitted on withoutany effort and subsequently can be pushed onto the precisely fittingouter jacket part 8 of the bearing support Part 7. For thecircumferential fixing and for preventing twisting, an axially extendinggroove 31 is provided in the inner bore of the stator iron core 9 and acorrespondingly adapted axial cam 35 (FIG. 5) is provided on the outerjacket 8.

The short area 34 of a smaller diameter at the outer jacket 8 of thebearing support part 7 will not be necessary, however, if the clearancebetween the inside diameter of the end plate 13 and the diameter of theouter jacket 8 is large enough to ensure a bending of the teeth 26 ofthe toothed disk.

The slightly conical shape of the outer jacket 8 of the bearing supportpart 7 caused by manufacturing is eliminated by at least three ribs 36(FIG. 5) which are parallel to the axis of the bearing support 7 andwhich are molded on and distributed over its circumference. This furtherimproves the centering and the alignment of the stator 3, 23 withrespect to the bearing bore 37 Ribs 38, which are parallel to the axisand center the bearings 5, 6 to be inserted, are injection-molded onalso at the wall of the bearing bore 37 which is made conical.

FIGS. 4 and 5 show a typical fan application of electric motorsaccording to the invention. The axial fan consists of a one-pieceplastic injection-molded housing 40 which contains the flange 10, webs45, 46 and the bearing support part 7. An impeller 41 with blades 42 formoving the air current through a flow duct 43 is mounted on the rotor 2Such fans are very compact (the representation in these FIGS. 4, 5 isapproximately twice the size of the object itself) and as amass-produced product, are simple and reasonable in price. The stator 3,which previouslY had been mounted by means of gluing, is replaced by thestator 23 which, according to the invention, can be mounted in a simplerand more secure manner. This reduces the costs even more, which isimportant for this type of a mass-produced product.

When the stator is pressed by a force Fl on the interior area of thebundle of plates of the stator iron core 9, the bundle of plates is bentdownward by means of a counterpressure by force F2. During spring-back,the teeth 26 are additionally pressed into the outer jacket 8,eliminating any axial play.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example only, and is not to be taken by way oflimitation. The spirit and scope of the present invention are to belimited only by the terms of the appended claims.

I claim:
 1. An electric motor having:a fastening flange; a bearingsupport part made of deformable material; a rotor surrounding a stator;the stator having winding end plates and an iron core axially securedabout an outer diameter of the bearing support part at a side facingaway from the fastening flange; a toothed disk having a central boresurrounding the diameter of the bearing support part and having radiallyinwardly projecting projection means which are in external contact withthe bearing support part to axially fasten the stator to the bearingsupport part; wherein the toothed disk has at least one tongue meansprotruding beyond an outer edge thereof for connecting and aligning thetoothed disk to the stator; and wherein the toothed disk is held betweena winding end plate and the iron core of the stator by an electricalwinding.
 2. An electric motor according to claim 1, wherein the radiallyinwardly projecting projection means of the toothed disk is constructedas pointed teeth.
 3. An electric motor according to claim 1, wherein thestator iron core is constructed as a bundle of plates with an axiallyextending groove in an inside bore of the plates for rotatably securingthe plates to the bearing support part.
 4. An electric motor accordingto claim 1, wherein the bearing support part has an axially extendingcam means on an outer surface for rotatably securing the stator to thebearing support part.
 5. An electric motor according to claim 1, whereinat least three axially extending positioning rib means are arranged onthe outer surface of the bearing support part and in parallel to itsaxis for positioning the bearing support part with respect to thewinding plates.
 6. An electric motor according to claim 1, wherein at anend of the bearing support part, at the side facing away from theflange, the bearing support part has a short axial area of a smallerdiameter.
 7. An electric motor according to claim 1, wherein the rotordrives an axial fan,a housing for the fan including said fasteningflange, said bearing support part and a plurality of webs; and wherein afan impeller is fastened on said rotor and is mounted centrically in aflow duct of the housing.
 8. An electric motor according to claim 2,wherein the pointed teeth are resilient and are flexed by the bearingsupport part.
 9. An electric motor according to claim 8, wherein thebearing support part has a reduced diameter portion to accommodateflexure of the pointed teeth.
 10. An electric motor according to claim1, wherein a support means extends from one of the winding plates toposition that winding plate with respect to the fastening flange.
 11. Anelectric motor according to claim 1, wherein a support means extendsfrom one of the winding plates to support an electrical circuit boardcontaining a motor control circuit.
 12. An electric motor according toclaim 1, wherein one of the winding plates has a radial outer portionthat insulatingly covers a portion of the iron core.
 13. An electricmotor according to claim 1, wherein the stator core is constructed as abundle of plates, and wherein at least one of these plates has a radialinward portion that is bent axially to provide a force to the projectionmeans of the toothed disk when the toothed disk is held by the windingend plates.
 14. An electric motor according to claim 1, whereinreinforcement ribs are located on the winding end plates and wherein theribs are utilized to receive an external assembly force to assist in themounting of the winding end plates.
 15. An electric motor according toclaim 1 wherein radially directed internal ribs are located on aninternal surface of the bearing support part for centering the bearingsupport with respect to a supported bearing.
 16. An electric motoraccording to claim 1, wherein the toothed disk is made of spring steeland has a thickness of approximately 0.1 to 0.3 mm.
 17. An electricmotor according to claim 16, wherein the radially inwardly projectingprojection means of the toothed disk is constructed as pointed teeth.18. An electric motor according to claim 16, wherein the stator ironcore is constructed as a bundle of plates with an axially extendinggroove in an inside bore of the plates for rotatably securing the platesto the bearing support part.
 19. An electric motor according to claim 16wherein the bearing support part has an axially extending cam means onan outer surface for rotatably securing the stator to the bearingsupport part.
 20. An electric motor according to claim 16 wherein atleast three axially extending positioning rib means are arranged on theouter surface of the bearing support part and in parallel to its axisfor positioning the bearing support part with respect to the windingplates.
 21. An electric motor according to claim 16 wherein at an end ofthe bearing support part, at the side facing away from the flange, thebearing support part has a short axial area of a smaller diameter. 22.An electric motor according to claim 16 wherein the rotor drives anaxial fan,a housing for the fan including said fastening flange, saidbearing support part and a plurality of webs; and wherein a fan impelleris fastened on said rotor and is mounted centrically in a flow duct ofthe housing.
 23. An electric motor according to claim 17, wherein thepointed teeth are resilient and are flexed by the bearing support part.24. An electric motor according to claim 23, wherein the bearing supportpart has a reduced diameter portion to accommodate flexure of thepointed teeth.
 25. An electric motor according to claim 16, wherein asupport means extends from one of the winding plates to position thatwinding plate with respect to the fastening flange.
 26. An electricmotor according to claim 16, wherein a support means extends from one ofthe winding plates to support an electrical circuit board containing amotor control circuit.
 27. An electric motor according to claim 16,wherein one of the winding plates has a radial outer portion thatinsulatingly covers a portion of the iron core.
 28. An electric motoraccording to claim 16, wherein the stator core is constructed as abundle of plates, and wherein at least one of these plates has a radialinward portion that is bent axially to provide a force to the projectionmeans of the toothed disk when the toothed disk is held by the windingend plates.
 29. An electric motor according to claim 16, whereinreinforcement ribs are located on the winding end plates and wherein theribs are utilized to receive an external assembly force to assist in themounting of the winding end plates.
 30. An electric motor according toclaim 16 wherein radially directed internal ribs are located on aninternal surface of the bearing support part for centering the bearingsupport with respect to a supported bearing.
 31. An electric motorhaving:a fastening flange; a bearing support part made of deformablematerial; a rotor surrounding a stator; the stator having winding endplates and an iron core axially secured by a first securement meansabout an outer diameter of the bearing support part at a side facingaway from the fastening flange and comprising plates which are axiallysecured by a second securement means; a toothed disk having a centralbore surrounding the diameter of the bearing support part and havingradially inwardly projecting projection means which are in externalcontact with the bearing support part to axially fasten the stator tothe bearing support part; wherein the toothed disk has at least onetongue means protruding beyond an outer edge thereof for connecting andaligning the toothed disk to the stator; and wherein the toothed disk isheld between the a winding end plate and the iron core of the stator bythe second securement means.
 32. An electric motor according to claim31, wherein the toothed disk is made of metal and has a thickness ofapproximately 0.1 to 0.3 mm.